The present invention relates to the use of organo-tin esterification catalysts in the production of polyester and polyester-containing compositions, and more particularly to the use of non-toxic catalysts to produce non-toxic compositions suitable for use in food, beverage, pharmaceutical, and medical-device applications.
It is well known that organotin compositions, including organotin oxides, hydroxides, alkoxides and carboxylates, are effective as catalysts in the manufacture of polyester resins and polyester-containing compositions. The use of tin catalysts in the esterification of polyesters is discussed in U.S. Pat. Nos. 2,720,507 issued to Caldwell et al, 3,345,339 issued to Parker et al, and 4,554,344 issued to Jackson et al. The organotin catalysts decrease the time required to complete esterification or transesterification and to effect complete reaction.
Polyester resins and compositions are useful in the manufacture of textiles, coatings, packaging and molded articles. A major application area is in the production of coatings and packages for storing and handling of foods, beverages, and pharmaceuticals and as components of medical devices. When used in such applications, the polyester compositions, and the articles made therefrom, need to be "non-toxic", that is, safe for use by consumers when used for their intended purpose. The compositions and their components generally require the approval of appropriate health-regulatory agencies, such as the U.S. Food and Drug Administration (USFDA). To obtain such approval, prospective users often have to conduct extensive tests, which are both time-consuming and expensive.
Organotin catalysts of the type employed herein have not yet been publicly sanctioned by the USFDA for use in the manufacture of polyesters intended for regulated "food-grade" (as defined by the USFDA) uses, such as food, beverage and pharmaceutical handling and packaging, or medical devices which come into contact with body fluids. Therefore, manufacturers of regulated food-grade polyester resins and polyester-containing compositions, as well as those who fabricate regulated articles therefrom, may resort to less-efficient catalysts or use no catalyst at all. However, the use of less-efficient catalysts, or no catalysts at all, can result in long reaction times with increased costs and energy consumption.
Some users have relied on the assumption that there is zero extraction of the catalyst from contact surfaces into foods, beverages, pharmaceuticals, and body fluids, and that therefore the catalyst is not a "food additive" (as defined by the USFDA), and requires no regulatory sanction. This is, however, an untenable position. Reliance on the assumption of zero extraction of the catalyst from such polyester articles without further testing is faulty, because the extractability of such catalysts from polyester articles into the wide variety of foods, beverages, pharmaceuticals, and body fluids with which they may come into contact is not known, particularly for articles intended for repeated use.
A more desirable situation is one in which the toxicity and extractability of the catalyst has been fully explored and reviewed by scientists experienced in chemistry, polymerization and toxicology so that a scientific judgment can be made and regulations can be published by the appropriate regulatory agency for general use by the public. Such regulations can state the composition of the catalyst material, the purity of the catalyst, the polyester resins and compositions in which the catalyst may be used, acceptable use levels of the catalyst, extraction testing procedures, and extraction limitations. Where the evidence submitted to the regulatory agency clearly demonstrates that the catalyst is of exceptionally low toxicity and only extractable in minute amounts under representative conditions of use in finished articles, the regulatory agency, for example, the USFDA, may conclude that the catalyst material may be used for its intended technical effect without requiring additional extraction testing by particular users, such as polyester manufacturers and article fabricators.